1. Field of the Invention
The present invention relates to a vehicle brake hydraulic pressure control unit which is characterized in a mounting construction of assembled parts such as an electromagnetic valve, a pump, a pressure sensor and the like and, a method for producing the same control unit.
2. Description of Related Art
There are known vehicle brake fluid control units which include a base body which incorporates therein a brake fluid flow path and assembled parts such as an electromagnetic valve, a pump, a pressure sensor and the like as vehicle brake hydraulic pressure control units for controlling the magnitude of a brake hydraulic pressure applied to wheel brakes (for example, Japanese Patent Unexamined Publications Nos. JP-A-2001-280533 and JP-A-2005-133934).
Incidentally, in JP-A-2001-280533 and JP-A-2005-133934, an electromagnetic valve, which is one of the assembled parts, is assembled into a bottomed mounting hole portion which is provided in the base body in such a manner as to communicate with the flow path in the interior of the base body. In addition, in JP-A-2001-280533 and JP-A-2005-133934, a lower end portion of the electromagnetic valve is inserted into a lower portion of the mounting hole portion for subsequent clamping process, and a plastically deformed portion is thereafter formed on a hole wall of the mounting hole portion by pressing the surface of the base body around the circumference of an opening in the mounting hole portion. Then, the plastically deformed portion so formed is caused to enter a locking groove formed on an outer circumferential surface of the electromagnetic valve to thereby prevent the dislocation of the electromagnetic valve from the mounting hole portion.
In the vehicle brake hydraulic pressure control unit of JP-A-2001-280533, the outside diameter of the electromagnetic valve is made identical at an upper side of the locking groove (an opening side of the mounting hole portion) and a lower side thereof (a bottom surface side of the mounting hole portion). Therefore, when a force is applied in a direction in which the electromagnetic valve is pushed out from the mounting hole portion by virtue of brake hydraulic pressure, there is caused a fear that a shear fracture plane is generated in a proximal end portion of the plastically deformed portion which protrudes into the interior of the locking groove. Namely, in the vehicle brake hydraulic pressure control unit of JP-A-2001-280533, since the assembling strength of the electromagnetic valve (the resisting force which resists the extruding force by virtue of brake hydraulic pressure) is dependent on the groove width of the locking groove, when the groove width of the locking groove is decreased, the assembling strength of the solenoid is also decreased. Namely, when attempting to realize a reduction in size of the electromagnetic valve by reducing the size of the locking groove as disclosed in JP-A-2001-280533, the assembling strength of the electromagnetic valve has to be sacrificed. In addition, in the vehicle brake hydraulic pressure control unit of JP-A-2005-133934, as well, since the outside diameter of the electromagnetic valve is made identical at an upper side and a lower side of the locking groove, when attempting to realize a reduction in size of the electromagnetic valve by reducing the size of the locking groove, the assembling strength of the electromagnetic valve has to be sacrificed.
In addition, when the outside diameter of the electromagnetic valve is made identical at the upper side and the lower side of the locking groove, since the plastically deformed hole wall is brought into close contact with the outer circumferential surface of the electromagnetic valve which lies further upwards than the locking groove immediately after the hole wall of the mounting hole portion starts the plastic deformation, the clamping load has to be increased.
Note that the aforesaid problem is not limited to the case where the assembled part is the electromagnetic valve but commonly applies to a case where the assembled part is a pump, a reservoir, a pressure sensor or the like.